Triggering Emails from a Date Field/Column

Question

Hi, my question is actually for SP 2010 not 2013.  I am looking to trigger automatic emails to document authors when pre-alert point dates are met i.e. a document due for review, for example on the 20th of the month the Author receives and email reminding them 20 days before and a further reminder 10 days before.

I have set formulas to calculate the 20 and 10 day before next review dates, so I have the dates Column/Field triggers but I need to know formula solution to then trigger a template email to the associated document Author (a separate columm with Authors email address is also existent).  So need something (I assume ) along the lines of.............

 

=[Trigger Date 20 ]=Today, email [Author] 20 Day prior email template.......... 

 

=[Trigger Date 10 ]=Today, email [Author] 10 Day prior email template..........

 

I have looked but cannot find any email trigger formulas like the above and I have also looked at Workflow but cannot see anything that appears will meet my requirements.

 

Any guidance would be greatly appreciated

 

Thank you

 

Mike